The invention relates to flow control devices having one or more shiftable valve members. More particularly, the invention relates to apparatus and methods for moving a shiftable valve member from an open to a closed position.
Fluid flow operations often involve the use of flow control devices having shiftable valve members that can be opened and closed to control fluid flow thereby. Mechanisms are thus necessary to enable movement of the shiftable valve members from open to closed positions. For example, conventional oil and gas well operations commonly utilize flow control devices that can be closed to shut off fluid flow and opened to allow fluid flow thereby, or otherwise provide access into and through the flow control device. For a particular example, flapper type safety valves are commonly located in well tubing and include a flapper member movable between open and closed positions.
Mechanisms for closing flow control devices have been proposed. For example, U.S. Pat. No. 4,624,315 to Dickson et al., 4,411,316 to Carmody, 3,786,866 to Tausch et al. and 4,660,646 to Blizzard each discloses a spring engaged with the shiftable flapper member of a flapper type valve assembly and disposed around a hinge pin to bias the flapper member into a closed position. U.S. Pat. No. 5,137,090 to Hare et al. discloses a curved beam type spring mounted within the tubular body of a flapper valve and an arm that engages the flapper member for yieldably urging the flapper member toward its closed position. For yet another example, U.S. Pat. No. 4,531,587 to Fineberg discloses the use of a pair of helical torsion springs engaged with hinge pins which are integral to the flapper member for biasing a flapper member to its closed position.
With respect to each of the above-cited patents, it is important to understand that the features mentioned above are merely examples of features disclosed in the patents. There are numerous other features disclosed in each patent in addition to the features mentioned herein. The additional features can be readily understood from a thorough review of each respective patent. The brief discussion above is included only to introduce the subject matter of the patents and not to distinguish the same from the present invention. Therefore, it is the patent applicant's intent that the brief remarks above about the cited patents not, in any way, limit or affect the scope of any of the appended claims. A comparison of any of the above-cited patents with the invention of any of the appended claims should involve a comparison of all features of the cited patent together as compared with the entirety of the selected claim(s).
In considering existing technology for closing the shiftable valve member of a flow control device, there remains a need for apparatus and methods having one or more of the following attributes: ensuring the shiftable valve member remains closed when in a closed position; an apparatus that is strong and reliable in the environment within which it is used; an apparatus that may be used in a dual spring configuration to provide added biasing force for yieldably urging the shiftable valve member in a closed position; an apparatus that requires or occupies minimal or no additional length in the flow control device or the conduit within which the flow control device is located.